1. Field of the Invention
The invention relates to a self-boosting electromechanical vehicle brake.
2. Description of the Prior Art
A mechanically actuated self-boosting friction brake is disclosed in European Patent Disclosure EP 299 593 A1. The known friction brake is embodied as a multiple disk brake, with a number of coaxially disposed friction disks, which for braking can be pressed by an actuating device against a brake body, which may also be embodied in multiple parts. The friction disks can also be called friction braking elements. In the known friction brake, the brake body has a drumlike housing, which forms a reservoir for a coolant and/or lubricant fluid. The terms friction braking element and brake body are intended here to refer in general to elements of a brake of which one is fixed and the other is rotatable and which are pressed against one another for braking, so that the fixed element brakes the rotatable element by friction.
The actuating device of the known friction brake has two spreader rings, which are disposed coaxially next to one another and coaxially to the friction disks between two of the friction disks. On end faces oriented toward one another, the spreader rings have rampways, in which balls, as roller bodies, rest. The rampways extend in the circumferential direction, and their depth increases in both circumferential directions; that is, the rampways rise in both circumferential directions. For actuation, the spreader rings are rotated counter to one another, causing the balls to roll in the rampways. Because of the upward slope of the rampways, the balls press the spreader rings apart in the process. As a result, the spreader rings, which can be thought of as parts of the brake body, are pressed against of two of the friction disks, which in turn are pressed against further parts of the brake body, in particular against the housing, and as a result are braked.
When pressed upon, the rotating friction disks exert a frictional force on the spreader rings in the direction of rotation, and this force urges the spreader rings in the actuation direction. As a result, a moment is exerted on the spreader disks that increases their rotation and hence the spreading force and pressure force. The spreader rings, which form part of the actuating device, thus at the same time form a self-boosting device, which converts a frictional force, exerted on it by the friction disks that form the friction braking elements, into a pressure force and as a result increase the braking force.